1. Field of the Invention
The invention pertains to manufacture of linerboard for corrugated boxes. More particularly the invention relates to a process wherein high yield cellulosic pulp may be substituted for a portion of more expensive conventional Kraft chemical pulp to manufacture linerboard for corrugated boxes.
2. Brief Description of the Prior Art The prior art literature is replete with descriptions of the preparation of paper forming pulps from lignocellulosic materials such as wood chips. The art itself is one of the most ancient. In spite of the antiquity of the art, new discoveries the objectives have been to advance the art in respect to greater economy; i.e., reducing costs by extending the pulp yield of the wood chips used in the pulping process, thereby reducing wood procurement costs and increasing recovery boiler capacity.
One of the problems associated with the use of high yield softwood fiber pulp in the manufacturing of linerboard has been the weakness of the product sheets. The final strength properties of linerboard formed from these high yield pulps are unacceptable in the marketplace. Replacement of the more expensive chemical pulp with high yield pulp substitutes has heretofore been limited to about 15% by weight, in the manufacture of linerboard. This results from the fact that as the percent of high yield pulp substitutes increased, the crush strength of the linerboard product decreased.
This invention allows for the manufacture of linerboard by substitution of a chemical pulp with up to 40% by weight of a high yield chemically treated softwood pulp, while still maintaining substantially the same crush strength as a linerboard sheet made from an all pine wood chemical pulp.